To evaluate window defrosting performance, certain standard operating procedures have been developed for vehicles of any power plant type, including gas, diesel, electric/hybrid (HEV, PHEV, BEV) and others. For example, one procedure followed by the automotive industry establishes a uniform test procedure and performance requirements for vehicle window defrosting systems that can be conducted on uniform test equipment in commercially available laboratory facilities, for example for buses [Society of Automotive Engineers (SAE) Surface Vehicle Recommended Practice, SAE J381, SAE International, Warrendale Pa., 2000) and for automobiles (SAE J902), with other comparable standards for vehicle window defrosting and defogging established worldwide, see for example FMVSS103 (North America), ADR42/04 (Australia), GB 11555-2009 (China), and ECE 672/2010 (Europe), the contents of each of which are incorporated in their entirety by reference herein as if fully reproduced. Such testing is necessary for comparing alternative defroster systems during the automotive design process, and/or for comparing defroster performance of a vehicle/engine configuration to an established standard.
Further, uniform testing protocols such as SAE J381 and J902 provide for established minimum standards for window defrosting/demisting within a predetermined time period. To assist in making these evaluations, predetermined templates representing areas of a window such as a windshield that must be fully or partially defrosted over the predetermined time period have been defined. These templates are often a part of the regulatory requirements established by government agencies, and define specific vehicle occupant vision zones of a window that are required to be defrosted within a specific time period after the vehicle engine and defrost system are started.
At a high level, the uniform test procedure requires a vehicle soaking step (for example, 10 hours at −18° C. for defrosting, −5° C. for defogging). In the case of defrosting, this is followed by an additional application of a predetermined amount of water to create a substantially uniform coating of frost/ice on the vehicle windows. Next, a predetermined air flow is initiated such as in a wind tunnel, and the vehicle engine and defrost system are started to begin defrosting of the window glass. In one part of the conventional test procedure, human intervention is required, that is, traces are taken by outlining ice areas of a window using a wax pencil or the equivalent at predetermined intervals over a predetermined time period (or until the window is determined to be clear of frost/ice), and once the test is completed those traces are transferred to paper by tracing, reduced, and analyzed by a known computer program product (for example, MATLAB; Mathworks, Natick, Mass.) in order to measure/calculate the defrosting/defogging area.
The steps of tracing and transferring prior to calculation introduce significant potential for human error due to the operator subjectivity required to transfer a trace and convert it into a usable format. Moreover, the vehicle must be transferred to a warm area in order to allow transfer of the trace to paper. This reduces the number of tests that can be performed consecutively. Also, paper used to transfer a windshield trace must be quite large to match typical windshield dimensions. For this reason it is often the case that traces that have been transferred to paper must be analyzed/measured outside of the laboratory facilities, since most testing facilities do not have an image reducer that can handle paper of the required dimensions for a vehicle window tracing.
It is also known to utilize digital cameras to record window defrosting performance (SAE J381, 2000). Images taken by each camera are downloaded to a computing device equipped with suitable software according to the particular cameras used. Then, the images are printed and an ice area is calculated for each image, such as by a planimeter. Again, the steps of calculating ice areas on images, such as for windows having different defrost states including areas of white ice, gray ice, wet ice, an edge of wet ice, and a fully defrosted area, allow for the introduction of human error in the process. In turn, simply analyzing printed images for ice areas does not account for certain factors that may influence the test results, such as errors/artifacts introduced during the photographic processes due to window curvature, size reduction, etc., and so may introduce further error into the results obtained by the testing process.
To address these and other issues, the present disclosure describes a system and method for monitoring and evaluating performance of a vehicle window defroster and defogger. Advantageously, the system and method provide automatic comparison of defrosting performance against a predetermined template which can represent regulatory standards for window defrosting and defogging, including accounting for irregularities in window shape and size during the process of image acquisition/analysis. The system and method further include automatic monitoring/optimizing of lighting to maximize efficiency of monitoring/analyzing window defrosting performance.